1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus for imaging organs and so on within a living body by transmitting and receiving ultrasonic waves to generate ultrasonic diagnostic images to be used for diagnoses.
2. Description of a Related Art
In medical fields, various imaging technologies have been developed for observation and diagnoses within an object to be inspected. Especially, ultrasonic imaging for acquiring interior information on the object by transmitting and receiving ultrasonic waves enables image observation in real time and provides no exposure to radiation unlike other medical image technologies such as X-ray photography or RI (radio isotope) scintillation camera. Accordingly, ultrasonic imaging is utilized as an imaging technology at a high level of safety in a wide range of departments including not only the fetal diagnosis in obstetrics, but also gynecology, circulatory system, digestive system, and so on.
The principle of ultrasonic imaging is as follows. Ultrasonic waves are reflected at a boundary between regions having different acoustic impedances such as a boundary between structures within the object. Therefore, by transmitting ultrasonic beams into the object such as a human body, receiving ultrasonic echoes generated within the object, and obtaining reflection points where the ultrasonic echoes are generated and reflection intensity, outlines of structures (e.g., internal organs, diseased tissues, and so on) existing within the object can be extracted.
Generally, in an ultrasonic diagnostic apparatus, an ultrasonic probe including plural ultrasonic transducers (vibrators) having transmitting and receiving functions of ultrasonic waves is used. Reception signals outputted from the vibrators that have received ultrasonic echoes have delays according to differences of distances between the focus of ultrasonic waves and the respective vibrators. Accordingly, beam forming processing (reception focusing processing) of forming a focus in a specific position is performed by providing the delays according to the positions of the vibrators to those reception signals and adding those reception signals to one another. In this regard, until the reception signals are added to one another, those reception signals are treated as parallel data.
The reception focusing processing is typically performed by digital signal processing. That is, the A/D-converted reception signals are accumulated in a memory and read out while the readout times are changed as needed, and appropriately interpolated and added to one another. When the reception signals are added to one another, the number of channels of signals becomes single, and signal transfer can be performed by wireless communication. Therefore, by incorporating a circuit for performing reception focusing processing into the ultrasonic probe, the number of signal lines connecting between the ultrasonic probe and an ultrasonic diagnostic apparatus main body can be reduced, and further, wireless communication can be realized.
However, in the reception focusing processing, since amounts of delay to be provided to the reception signals vary depending on the position of the focus, control of the readout times from the memory is extremely complex and a large-scaled circuit is necessary. If such a circuit is incorporated into the ultrasonic probe, the probe size becomes not the practical size that can be operated with one hand. Further, since the ultrasonic diagnostic apparatus main body receives data after beam forming and sequentially generates images based on the data, when transfer quality is poor, there is a problem that a moving image cannot be generated smoothly due to reception delay of data with respect to a certain line or the like.
As a related technology, Japanese Patent Application Publication JP-P2003-299648A discloses an ultrasonic diagnostic apparatus having an ultrasonic probe by which a transfer cable can be made thinner and lighter even when the number of vibrating elements increases with higher definition, and maintenance and improvement of operability can be realized. The ultrasonic diagnostic apparatus includes an ultrasonic probe for performing transmission and reception of ultrasonic pulses for a living body by using plural vibrating elements, and an apparatus main body connected to the ultrasonic probe via a transfer cable, for generating transmission signals for transmitting ultrasonic pulses from the ultrasonic probe and forming an ultrasonic image from reception signals based on ultrasonic pulses (echoes) reflected by the living body and received by the ultrasonic probe. The ultrasonic diagnostic apparatus is characterized in that the transmission signals and reception signals transferred between the ultrasonic probe and the apparatus main body via the transfer cable are time-divisionally sectioned into chips for each vibrating element before transfer, and the respective chips are sequentially transferred by using a common signal line within the transfer cable.
However, in the ultrasonic diagnostic apparatus according to JP-P2003-299648A, the reception signals outputted from the respective vibrating elements are transferred in the unchanged frequency band, and therefore, the data volume cannot be reduced and a high transfer rate is necessary. Further, since the reception signals are time-divisionally transferred, there is no guarantee that the beam forming processing can be performed reliably after transfer.
Japanese Patent Application Publication JP-P2002-85405A discloses an ultrasonic diagnostic apparatus for the purpose of improvements in workability of ultrasonic examiners such as an improvement of operability of an ultrasonic probe. The ultrasonic diagnostic apparatus is constituted to be physically separable into (i) an ultrasonic collecting/operating unit having ultrasonic transducers, ultrasonic signal transmitting and receiving means for transmitting and receiving ultrasonic signals between an object to be inspected and itself via the ultrasonic transducers, ultrasonic beam forming means for generating ultrasonic beam data from output of the ultrasonic signal transmitting and receiving means, signal processing means for converting the ultrasonic beam data into data for generating image data, wireless communication means for transmitting the converted ultrasonic beam data as a wireless signal, and operating means for controlling ultrasonic signal collection, and (ii) an ultrasonic image generating and displaying unit having wireless receiving means for wirelessly receiving the ultrasonic beam data, image generating means for generating image data from the ultrasonic beam data, and image display means for displaying the image data.
However, in the ultrasonic diagnostic apparatus according to JP-P2002-85405A, the reception signals outputted from the plural ultrasonic transducers are serialized after beam forming, and therefore, a front-end circuit as a whole in a conventional ultrasonic diagnostic apparatus should be accommodated within the ultrasonic collecting/operating unit. Therefore, not only the circuit scale is huge but also a high transfer speed for serial communication is required.
Japanese Patent Application Publication JP-P2008-18107A discloses a wireless ultrasonic diagnostic apparatus for performing wireless transfer between an ultrasonic probe and an apparatus main body. In the ultrasonic diagnostic apparatus, the ultrasonic probe includes plural vibrators, amplifiers and A/D converters corresponding to the plural vibrators, a digital beam former, a PS conversion unit, a control data insertion unit, a modulator, and a power amplifier. In the ultrasonic probe, digital beam forming processing is performed to generate phase-matched and added data, and further, the phase-matched and added data is parallel/serial converted.
However, in the ultrasonic diagnostic apparatus according to JP-P2008-18107A, the reception signals outputted from the plural vibrators are serialized after beam forming, and therefore, a front-end circuit as a whole in a conventional ultrasonic diagnostic apparatus should be accommodated within the ultrasonic probe. Therefore, not only the circuit size is huge but also a high transfer speed for serial communication is required.
U.S. Pat. No. 6,251,073 B1 and U.S. Pat. No. 6,773,399 B2 disclose an ultrasonic diagnostic apparatus for generating an ultrasonic image without deteriorating the resolution while a width of an ultrasonic beam to be transmitted from an ultrasonic transducer array is broadened to make a broad beam. In U.S. Pat. No. 6,251,073 B1 and U.S. Pat. No. 6,773,399 B2, however, there is no disclosure as to reducing an amount of data within an ultrasonic probe when reception signals are transferred from the ultrasonic probe to an ultrasonic diagnostic apparatus main body.